The present invention relates generally to the field of electrical enclosures. More particularly, the invention relates to a novel venting arrangement for an electrical enclosure that permits the escape and cooling of heated gasses resulting from faults and malfunctions within the enclosure.
A wide range of applications exist for electrical enclosures and cabinets. Such enclosures include both small and large individual units, such as for housing contactors and other switchgear. Larger enclosures are also common, such as for housing various power electronics equipment, control circuits, motor drives, and so forth. For instance, in industry it is common to find large enclosures divided into bays or segments for single and three-phase switchgear, motor controllers, programmable logic controllers, data and power network interfaces, and so forth.
A particular challenge in the design and operation of electrical components in enclosures relates to channeling and cooling of hot gasses that can result from malfunction of the electrical components. Relatively low level electronic signals exhibit fault characteristics that do not produce volumes of hot gasses. However, in applications where higher voltage electrical power is routed to devices, particularly through fuses, disconnects, contactors, switchgear, controllers and so forth, certain types of fault can produce arcs that can heat and even vaporize neighboring components. While development of protective circuitry has focused on interrupting such faults extremely quickly, even several cycles of alternating current can suffice to vaporize wires, insulation, and even component housings. Such faults result in large volumes of hot gas that expand and must be channeled or vented within or from the enclosure.
Enclosure venting techniques have been developed that can route hot gasses from an enclosure during a fault. Certain of these include large air conduits that can lead gasses away from the enclosure, such as to an external environment outside of a factory. Enclosures have also been designed that allow a door or other cover to be displaced (e.g., blown partially out) by hot gasses to permit the gasses to escape. Such techniques are either quite expensive, or fairly destructive to the enclosure, or both. In many cases, it is preferred to vent hot gasses as quickly as possible, and to cool the gasses regardless of the long term effects on the electrical components themselves, many of which may require replacement after the event.
A range of applications exist for vented electrical enclosures that simply cannot use these approaches to arc flash gas management. In vented enclosures, a vent is commonly provided for the exchange of air between the interior and the exterior of the enclosure with many such applications calling for forced air venting through the use of fans. Vented enclosures have faced a difficulty in dealing with arc flash faults, however, due to their inability to properly vent and cool gasses during such faults. Accordingly, vented enclosures capable of meeting industry standards for arc flash testing are not generally available.
There is a need, therefore, for improved designs for enclosures and improved techniques for venting gasses from such enclosures upon occurrence of a fault condition. There is a particular need for designs that can meet stringent industry standards for gas temperatures around the enclosure, while permitting conventional venting of the enclosure.